The Internet is increasingly being used to support mobile applications. There a growing need to support many different types of microflows, including both real-time and non real-time services.
In a mobile environment, microflows emanating from a Mobile Node (MN) are characterized by a set of parameters. The parameters define a context and the resulting feature contexts may be stored within an access router (AR).
Some features are specifically defined for a particular microflow, while others are defined for all the microflows belonging to the MN. These features may be for defining the QoS state, (such as RSVP, DiffServ, COPS), maintaining robust header compression, (such as van Jacobson and GRE), and security, (such as PKI and AAA). In order to assist in preserving the network bandwidth, it is desirable to store these parameters at some node entity within the access network, instead of at the MN itself. By doing that, the overhead of processing and transmission delay from the MN to the AR is greatly reduced. This saves the transmission bandwidth through the radio link and makes the design of the MN much simpler.
The context transfer protocol is tightly integrated into the handover protocols currently developed by the IETF, such as: Fast Handovers for Mobile IPv6, Low Latency Handoffs in Mobile IPv4, and Bi-directional Edge Tunnel Handover for IPv6. It must support seamless (i.e. uninterrupted), loss-less, resumption of services after the handover is completed. Therefore, an essential requirement of context transfer is that there must be good synchronization between the handover protocol and the context transfer method, and the context transfer must be reliable.
The protocol must maintain the integrity of data during the context transfer. There must be security association between the two ARs so that they can mutually authenticate themselves prior to the transfer of context. The context transfer protocol must also minimize the amount of processing at the sending and receiving ARs, and it must complete the context transfer with a minimum number of signaling messages.
It would also be desirable for the context transfer protocol to be scalable. Scalability means that the context transfer protocol should scale with the number of participating MNs, and that it should scale with the number of feature contexts and feature contexts being transferred.